The present invention relates to a substrate plating apparatus for performing a metal plating process on a substrate such as a semiconductor wafer.
FIG. 1 shows the general structure for this type of a conventional substrate plating apparatus. As shown in FIG. 1, a substrate plating vessel 101 accommodates a plating solution Q. Disposed within the substrate plating vessel 101 are a substrate 102, such as a semiconductor wafer; an anode 103 positioned opposite the substrate 102; and a shielding plate 104 interposed between the substrate 102 and anode 103. A power source 106 applies a predetermined voltage between the substrate 102 and anode 103 for forming a plating film on the surface of the substrate 102. A collecting gutter 105 is provided for collecting plating solution Q that overflows from the top end of the substrate plating vessel 101.
When using a soluble electrode (having phosphorus copper) for the anode 103 in the substrate plating apparatus described above, it is necessary not only to regularly replace the anode but also to process black film on the surface of the electrode and take measures for particles. Since this type of substrate plating apparatus is normally provided with a plurality of substrate plating vessels 101, upkeep of the anode 103 can be considerably time-consuming.
One method of attempting to correct these problems is to use an anode formed of an insoluble material in the plate processing vessel. While this material has the advantage of suppressing the existence of particles around the substrate 102, it gives rise to the necessity for replenishing Cu2+ ions. Cu2+ ions can be added by supplying copper oxide powder or CuSO4-5H2O powder, or by supplying a highly concentrated solution of CuSO4-5H2O. However, supplying powder is not appropriate for an automated process. Further, adding a solution gradually increases the overall amount of liquid, thus requiring that the plating solution be periodically discharged.
To improve the uniformity of the plating film thickness formed on the surface of the substrate 102 in the plating vessel described above, it is best to ensure that the primary current distribution between the cathode (substrate 102) and the anode 103 is uniform. One way to ensure a uniform distribution of the current is to increase the distance between the cathode and the anode 103. However, this requires a larger substrate plating vessel 101, and consequently, a larger plating apparatus, which is contrary to the object of decreasing the size of the plating apparatus.
When the electrolytic plating conducted is copper plating, for example, the soluble anode often includes phosphorus copper. However, it is difficult to manage the black film formed on the surface of this soluble anode, and the black film produces particle contaminants that can be a large problem. This problem can be overcome by using an insoluble anode. However, insoluble anodes give rise to the problem of how to supply Cu ions to the plating solution, as well as the problem of the additive dissolving and becoming deposited on the semiconductor wafer or other substrate.
In view of the foregoing, it is an object of the present invention to provide a substrate plating apparatus employing an insoluble anode, and particularly a substrate plating apparatus capable of easily and automatically supplying metal ions.
It is another object of the present invention to provide a substrate plating apparatus capable of supplying a uniform primary current distribution between the cathode and anode and facilitating reduction of the size of the plating apparatus.
It is further another object of the present invention to provide a plating apparatus capable of preventing the substrate from being contaminated by particles produced from black film, even when using a soluble anode.
These objects and others will be attained with a substrate plating apparatus for plating a substrate in accordance with the present invention. The substrate plating apparatus comprises a plating bath containing plating solution. A substrate is disposed in the plating bath and serves as a cathode. A insoluble anode is disposed in the plating bath opposite the substrate. A circulating vessel or dummy vessel is provided separate from the plating bath. A soluble anode is disposed in the circulating vessel or dummy vessel. A cathode is disposed in the circulating vessel or dummy vessel opposite the soluble anode. An anion exchange film or selective cation exchange film is disposed between the anode and cathode and isolates the same. And also provided is an ion replenishing system for creating a current between the anode and cathode to generate and supply metallic ions to the plating bath.
The substrate plating apparatus described above is constructed with a circulating vessel or dummy vessel separate from the plating bath, such that metal ions generated from the soluble anode in the circulating vessel or dummy vessel are supplied to the plating bath. With this construction, it is possible to supply metal ions automatically. Further, this construction eliminates the need to perform cumbersome jobs associated with conventional devices, such as regularly replacing the anode in the plating bath and taking measures to treat black film generated on the surface of the anode.
According to another aspect of the present invention, a substrate plating apparatus for plating a substrate comprises a plating bath containing plating solution. A substrate disposed in the plating bath. An anode disposed in the plating bath opposite the substrate. And, an ion exchange film or neutral porous diaphragm is disposed between the substrate and anode in the plating bath, wherein the ion exchange film or neutral porous diaphragm divides the plating bath into a substrate region and an anode region.
The ion exchange film or neutral porous diaphragm provided between the substrate and anode serves to increase the electrical resistance of the plating solution, achieving the same effects as increasing the distance between the substrate and the anode. Accordingly, it is possible to dispose the substrate and anode close together.
Further, the cation exchange film allows the passage of ions dissolved from the anode and blocks impurities dissolved from the anode. Accordingly, the amount of particles in the plating solution in the substrate region can be greatly reduced.